Sorptive interactions of Cu on soil, clay and humic acid

Department of Chemistry, Magadh University, Bodh Gaya-824 234, Bihar, India Manuscript received 6 August 2009, accepted 11 November 2009 Sorption and desorption of Cu on soils from four different locations of West Bengal have been studied. Sorption on humic acid and clays of the soils has also been measured. Measurements have been made at a pH or 6.0 without any back ground electrolyte. Comparison of sorption behavior of the soils have been made on the basis of the Langmuir parameters. One of the soils is very rich In organic matter and others are progressively poorer in it though richer in clay content. This enables us to make some guess on the role or each of the constituents on overall adsorption. Humic acids and clays Isolated from each soli have also been tested for adsorption efficiency. Adsorption maxima for all these constituents fall far below their individual CEC. Experiments have been done on soil residues after removal of mobile organic matter by alkali extraction. A drop in adsorption maxima has been observed although the decrease will not up to the theoretically calculated amount betraying a more complicated combined existence of humus and clay in native soil. Desorption experiment have been carried out in solutions of NaCl, KCl, MgCl2 and CaCl2. The desorbing efficiency of the ions was found to be in the decreasing order of Ca2+ > Mg2+ > > K+ > Na+. This result suggests predominantly an ion-exchange reaction